Electrochromic device

ABSTRACT

An electrochromic element composed of an ionically conductive substance layer containing a specified electrochromic substance sandwiched between two electrically conductive substrates at least one of which is transparent.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/JP98/05739 filed Dec. 18, 1998, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to electrochromic devices and more particularlyelectrochromic devices which are useful as light controllable windowsfor buildings, automobiles and passenger vehicles and various types oflight controllable glasses to be used for indoor decoration orpartitions; display devices; and antiglare mirrors for automobiles andother vehicles.

DESCRIPTION OF THE PRIOR ART

A conventional electrochromic device such as a light controllable glassof conventional type as disclosed in Japanese Patent Laid-OpenPublication No. 63-18336 is known which glass comprises a chromogenicmaterial in the form of a film obtained by sputtering orvacuum-depositing an inorganic oxide such as tungsten oxide (WO₃) over atransparent electrically conductive film.

However, the conventional film formation techniques must be carried outunder vacuum, resulting in increased production costs and a requirementof a large size vacuum apparatus if an electrochromic device of a largearea is intended to be produced. Furthermore, since a substrate isheated at an elevated temperature during sputtering, it is necessary toselect certain conditions if a substrate other than a glass, such as asynthetic resin made substrate is used, resulting in difficulties inreducing the weight of an electrochromic device.

There is also a problem that tungsten oxide can only make anelectrochromic device exhibit blue color.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electrochromicdevice which can be manufactured using an inexpensive color developingmaterial with easy operations and can easily be changed in color tone.

DETAILED DESCRIPTION OF THE INVENTION

An electrochromic device proposed by the present invention solves theabove-mentioned problems of the prior art by forming an ion conductivematerial layer containing a specified electrochromic material.

Namely, according to the present invention, there is provided anelectrochromic device comprising two conductive substrates, at least oneof which is transparent, and an ion conductive substance layer disposedtherebetween and containing an electrochromic substance represented bythe formula

wherein X⁻ and Y⁻ may be the same or different and are each a counteranion selected from the group consisting of a halogen anion, ClO₄ ⁻, BF₄⁻, PF₄ ⁻, CH₃COO⁻ and CH₃(C₆H₄)SO₃ ⁻ and R¹ and R² may be the same ordifferent and are each a hydrocarbon group having from 1 to 20 carbonatoms.

In the present invention, two electrically conductive substrates, atleast one of which is transparent, are used. The term “electricallyconductive substrate” designates substrates which have a function as anelectrode. Therefore, the conductive substrates used in the inventionencompass those entirely formed from an electrically conductive materialor formed with a non-electrically conductive substrate and an electrodelayer disposed thereon. Regardless of whether a substrate iselectrically conductive or not, it necessarily has a smooth surface atnormal temperature but may have a flat or curved surface and may bedeformable under stress.

At least of one of the two electrically conductive substrates is atransparent electrically conductive substrate and the other may be atransparent or opaque or reflective electrically conductive substrate.

Two conductive substrates both of which are transparent are suitable fora display device and a light controllable glass. A combination of atransparent conductive substrate and an opaque conductive substrate issuitable for a display device, while a combination of a transparentconductive substrate and a reflective substrate is suitable for anelectrochromic mirror.

The transparent conductive substrate is generally formed by laminating atransparent electrode layer over a transparent substrate. The term“transparency” used herein designates an optical transmission rangingfrom 10 to 100 percent.

The opaque conductive substrate is may be a laminate obtained bylaminating an electrode layer over one surface of a metal plate or anon-conductive opaque substrate such as various opaque plastics,ceramics, glasses, woods and stones.

The reflective electrically conductive substrate may be exemplified by(1) a laminate comprising a non-conductive transparent or opaquesubstrate and a reflective electrode layer formed thereon, (2) alaminate comprising a no-conductive transparent substrate having atransparent electrode layer on one of its surfaces and a reflectiveelectrode layer on the other surface, (3) a laminate comprising anon-conductive transparent substrate having a reflective layer formedthereon and further a transparent electrode layer formed thereon, (4) alaminate comprising a reflective substrate and a transparent electrodelayer formed thereon and (5) a plate-like substrate which itselffunctions as a reflective layer and an electrode.

No particular limitations is imposed on the transparent substrate whichmay thus be a color or colorless glass, a reinforced glass and a resinof color or colorless transparency. Specific examples of such a resininclude polyethylene terephthalate, polyamide, polysulfone, polyethersulfone, polyether etherketone, polyphenylene sulfide, polycarbonate,polyimide, polymethyl methacrylate and polystyrene.

The substrates used in the present invention must have a smooth surfaceat normal temperature.

There is no particular restriction to the transparent electrode layer aslong as it meets the requirements for achieving the purpose of thepresent invention. Specific examples of the electrode layer includeelectrically conductive film such as thin films of metals such as gold,silver, chrome, copper and tungsten or metal oxides such as ITO(In₂O₃—SnO₂), tin oxide, silver oxide, zinc oxide and vanadium oxide.

The electrode has a film thickness in the range of usually 100 to 5,000and preferably 500 to 3,000 angstrom. The surface resistance of theelectrode is usually in the range of 0.5-500 and preferably 1-50 Ω/sq.

No particular limitation is imposed on a method of forming the electrodelayer. Any suitable conventional methods may be employed, depending uponthe metal and metal oxide constituting the electrode. In general, theformation of the electrode layer is carried out by vacuum evaporation,ion plating, sputtering and a sol-gel method. The thickness of theelectrode layer is selected within the range such that the transparencythereof is not affected. The electrode layer may be partially providedwith an opaque electrode-activator for the purpose of impartingoxidation-reduction capability, electric conductivity and electricdouble layer capacitance, the electrode-activator being provided in anamount such that the transparency of the entire electrode layer is notharmed. Electrode activators eligible for the purpose of the inventionare a metal such as copper, silver, gold, platinum, iron, tungsten,titanium and lithium, an organic material having oxidation-reductioncapability such as polyaniline, polythiophen, polypyrrole andphthalocyanine, a carbon material such as active carbon and graphite anda metal oxide such as V₂O₅, MnO₂, NiO and Ir₂O₃ and mixtures thereof. Avariety of resins may be used for integrating the electrode activator inthe electrode. The opaque electrode activator may applied onto anelectrode by forming on an ITO transparent electrode a compositioncomprising an active carbon fiber, graphite and an acrylic resin into amicro pattern in the shape of stripes or by forming on a thin-film ofgold a composition comprising V₂O₅, acetylene black and butyl rubber inthe shape of a mesh.

No particular limitation is imposed on the reflective electrode layer aslong as it is stable electrochemically and has a specular surface.Eligible for the reflective electrode layer includes the films of metalsuch as gold, platinum, tungsten., tantalum, rhenium, osmium, iridium,silver, nickel and palladium and the film of an alloy such asplatinum-palladium, platinum-rhodium and stainless steel. The reflectiveelectrode layer is necessarily disposed onto a substrate or atransparent substrate with the reflectiveness and specularity of thelayer maintained. The reflective electrode layer is formed onto asubstrate by any suitable conventional method such as vacuum deposition,ion-plating and sputtering.

No particular limitation is imposed on a substrate on which thereflective electrode layer is disposed. The substrate may be transparentor opaque. Specific examples of the substrate include those asexemplified with respect to the transparent substrate described above, avariety of plastics, resins, glasses, woods and stones.

No particular limitation is imposed on materials for the above-mentionedreflective plate or layer as long as it can provide a specular surface.For example, silver, chrome, aluminum and stainless steel are eligible.

The plate-like substrate having a reflective layer and functioning as anelectrode may be exemplified by the substrates exemplified with respectto the reflective electrode among which are self-supportive.

The ion conductive material layer to be disposed between the twoconductive substrates is now described.

The ion conductive substance layer used in the present invention iscomposed of an ion conductive substance containing a specifiedelectrochromic substance.

In the present invention, the term “ion conductive substance” designatesa substance having an ion conductivity of 1×10⁻⁷S/cm or more at roomtemperature and playing a role of coloring, decoloring or discoloring anelectrochromic substance. No particular limitation is imposed on the ionconductive material, which may thus be liquid, gel or solid. Solid ionconductive substances are particularly preferred for the purpose of thea invention because an electrochromic device which is overall solid andexcelled in various performances for various practical usage can beobtained.

Liquid Ion Conductive Material

Eligible liquid ion conductive materials are those dissolving asupporting electrolyte such as salts, acids and alkalis in a solvent.

Although any suitable solvents may be used as long as they can dissolvea supporting electrolyte, preferred are those having polarity. Specificexample of such solvents are water and an organic polar solvent such asmethanol, ethanol, propylene carbonate, ethylene carbonate,dimethylsulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone,γ-valerolactone, sulforan, dimethylformamide, dimethoxyethane,tetrahydrofuran, propionnitrile, glutaronitlile, adiponitrile,methoxyacetonitrile, dimethylacetoamide, methylpyrrolidinone,dimethylsulfoxide, dioxolane, trimethylphosphate and polyethyleneglycol. Preferred are propylene carbonate, ethylene carbonate,dimethylsulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone,sulforan, dioxolane, dimethylformamide, tetrahydrofuran, adiponitrile,methoxyacetonitrile, dimethylacetoamide., methylpyrrolidinone,dimethylsulfoxide, trimethylphosphate and polyethylene glycol. These maybe used singlely or in combination.

Although not restricted, salts used as a supporting electrolyte may bealkali metal salts, inorganic ion salts such as alkaline earth metalsalts, quaternary ammonium salts and cyclic quaternary ammonium salts.Specific examples of such salts include alkali metal salts of lithium,sodium or potassium such as LiClO₄, LiSCN, LiBF₄. LiAsF₆, LiCF₃SO₃,LiPF₆, LiI, Nal, NaSCN, NaClO₄, NaBF₄, NaAsF₆, KSCN and KCl, quaternaryammonium salts or cyclic quaternary ammonium salts such as (CH₃)₄NBF₄,(C₂H₅)₄NBF₄, (n—C₄H₉)₄NBF₄, (C₂H₅)₄NBr, (C₂H₅)₄NClO₄ and (n—C₄H₉)₄NClO₄and mixtures thereof

Acids used as a supporting electrolyte may be exemplified by inorganicacids and organic acids, specific examples of which include sulfuricacid, hydrochloric acid, phosphoric acid, sulfonic acid carboxylic acid.

Alkalis used as a supporting electrolyte include sodium hydroxide,potassium hydroxide and lithium hydroxide.

Gelatinized-liquid Ion Conductive Material

The gelatinized-liquid ion conductive material may be those which aregelatinized or made to be viscous by adding a polymer or a gelatinizerto the above-mentioned liquid ion conductive material.

No particular limitation is imposed on the polymers, which thus may bepolyacrylonitrile, carboxymethylcellulose, polyvinyl chloride,polyethylene oxide, polyurethane, polyacrylate, polyamide,polyacrylamide, cellulose, polyester, polypropyleneoxide and nafion.

Preferred examples of the gelatinizers are oxyethylenemethacrylate,oxyethyleneacrylate, urethaneacrylate, acrylamide and agar-agar.

Solid Ion Conductive Material

No particular limitation is imposed on the solid ion conductive materialas long as it is solid at room temperature and ion conductive. Preferredexamples of such solid ion conductive materials are polyethyleneoxide,the polymer of oxyethylenemethacrylate, nafion, polystyrene sulfonate,Li₃N, Na-β-Al₂O₃ and Sn(HPO₄)₂H₂O. Particularly preferred are polymersolid electrolytes obtained by polymerizing a polyethyleneoxide-basedcompound, an oxyalkyleneacrylate-based compound or aurethaneacrylate-based compound.

First examples of such polymer solid electrolytes are those obtained bysolidifying a composition (hereinafter referred to as Composition A)containing the above-described organic polar solvent and supportingelectrolyte and a urethaneacrylate of the formula (2) below.

The term “cure” used with respect to the polymer solid electrolyte aswell as Composition B hereinafter described designates a state where apolymerizing or crosslinking component is cured with the progress ofpolymerization (polycondensation) or crosslinking and thus thecomposition does not flow at room-temperature. The composition thuscured has the basic structure in the form of network.

Formula (3) is represented by the formula

wherein R⁶ and R⁷ may be the same or different and are each a group offormula (3), (4) or (5) below, R⁸ and R⁹ may be the same or differentand are each a C₁-C₂₀, preferably C₂-C₁₂ divalent hydrocarbon residue, Yis selected from a polyether unit, a polyester unit, a polycarbonateunit and the mixed unit thereof and b is an integer from 1 to 100,preferably 1 to 50 and more preferably 1 to 20.

Formulae (3), (4) and (5) are represented by the formulae

wherein R¹⁰, R¹¹ and R¹² may be the same or different and are each ahydrogen atom or a C₁-C₃ alkyl group and R¹³ is a C¹-C₂₀, preferablyC₂-C₈ organic residue of divalent through quateivalent.

Specific examples of such organic residues are a hydrocarbon residuesuch as alkyltolyl, alkyltetratolyl and alkylene of the formula

wherein R¹⁴ is a C₁-C₃ alkyl group or hydrogen, c is an integer from 0to 6 and if c is 2 or greater, R¹⁴ groups may be the same or different.

The hydrocarbon residue may be a group part of which hydrogen atoms aresubstituted by an oxygen-containing hydrocarbon group such as a C₁-C₆,preferably C₁-C₃ alkoxy group and a C₆-C₁₂ aryloxy group.

Specific examples of R¹³ group in formulae (3) thorough (5) are thoserepresented by the following formulae:

Each of the divalent hydrocarbon residues represented by R⁸ and R⁹ informula (2) is exemplified by a divalent chain-like hydrocarbon group,an aromatic hydrocarbon group and an alicyclic-containing hydrocarbongroup. Specific examples of the chain-like divalent hydrocarbon groupare those represented by formula (6) above.

Specific examples of the aromatic hydrocarbon group andalicyclic-containing hydrocarbon group are those represented by thefollowing formulae:

wherein R¹⁵ and R¹⁶ may be the same or different and each are aphenylene group, a phenylene group having an alkyl subsutituent, acycloalkylene group and a cycloalkylene group having an alkylsubstituent, R¹⁷, R¹³, R¹⁹ and R²⁰ may be the same or different and eachare a hydrogen atom or a C₁-C₃ alkyl group.

Specific examples of the groups R⁸ and R⁹ in formula (3) are thoserepresented by the following formulae:

In formula (2), “Y” indicates a polyether unit, a polyester unit, apolycarbonate unit and mixed unit thereof. Each of these units isrepresented by the following formulae:

In formulae (a) through (d), R²¹ through R²⁶ may be the same ordifferent and are each a C₁-C₂₀, preferably C₂-C₁₂ divalent hydrocarbonresidue. Preferred for R²⁴ are C₂-C₆ divalent hydrocarbon residues.Preferred for R²¹ through R²⁶ are straight or branched alkylene groupsamong which methylene, ethylene, trimethylene, tetramethylene,pentamethylene, hexamethylene and propylene groups are preferred forR²³, and ethylene and propylene groups are preferred for R²¹, R²² andR²⁴ through R²⁶. The letter “e” in formula (a) is an integer from 2 to300, preferably 10 to 200, the letter “f” is an integer from 1 to 300,preferably 2 to 200, the letter “g” is an integer from 1 to 200,preferably 2 to 100, the letter “h” is an integer from 1 to 200,preferably 2 to 100 and the letter “i” is an integer from 1 to 300,preferably 10 to 200.

Each unit represented by formulae (a) through (d) may be a copolymer ofthe same or different units. Namely, if a plurality of R²¹ through R²⁶are present, the groups of each R²¹ thorough R²⁶ may be the same ordifferent. Preferred examples of the above-mentioned polymer arepolymers of ethyleneoxide and propyleneoxide.

The urethaneacrylate may be prepared by any suitable conventionalmethod. Urethaneacrylate of formula (3) has a molecular weight in therange from 2,500 to 30,000, preferably 3,000 to 20,000. Theurethaneacrylate has preferably 2-6, more preferably 2-4 polymerizationfunctional groups per molecule.

An organic polar solvent (organic nonaqueous solvent) is added in anamount of 100-200, preferably 200-900 weight parts per 100 parts of theurethaneacrylate. The addition of the organic polar solvent in a tooless amount would result in insufficient ion conductivity, while theaddition of the organic polar solvent in a too much amount would causereduced mechanical strength. The supporting electrolyte may be salts,acids or alkalis. The supporting electrolyte should be added in anamount of 0.1 to 30, preferably 1 to 20 weight percent of the organicpolar solvent.

Composition (A) is obtained by solidifying the above-described essentialcomponents, namely, urethaneacrylate, organic nonaqueous solvent andsupporting electrolyte. If necessary, any suitable optional componentsmay be added to Composition (A) as long as they are not obstructive tothe achievement of the purpose of the invention. Such components may becrosslinkers and photo- or thermal polymerization initiators.

Second examples of the polymeric solid electrolyte are polymeric solidelectrolytes obtained by solidifying a composition (hereinafter referredto as Composition (B)) comprising an organic polar solvent, a supportingelectrolyte, a monofunctional acryloyle-modified polyalkylene oxide offormula (17) below or a polyfunctional acryloyle-modified polyalkyleneoxide of formula (18) or (19) below.

Formula (17) is represented by the formula

wherein R²⁷, R²⁸, R²⁹ and R³⁰ may be the same or different and are eachhydrogen and an alkyl group having from 1 to 5 carbon atoms and j is aninteger of 1 or greater Specific examples of the alkyl group includemethyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl.Preferred for R²², R²³ and R³⁴ are hydrogen and a methyl group.Preferred for R³⁰ are hydrogen and methyl and ethyl groups.

The letter “j” in formula (17) is an integer of 1 or greater, usuallyfrom 1 to 100, preferably from 2 to 50 and more preferably from 2 to 30.

Specific examples of compounds represented by formula (17) are thosehaving 1-100, preferably 2-50 and more preferably 1-20 oxyalkyleneunits, such as methoxypolyethylene glycol methacrylate,methoxypolypropylene glycol methacrylate, ethoxypolyethylene glycolmethacrylate, ethoxypolypropylene glycol methacrylate,methoxypolyethylene glycol acrylate, methoxypolypropylene glycolacrylate, ethoxypolyethylene glycol acrylate, ethoxypolypropylene glycolacrylate and mixtures thereof.

If “j” is 2 or greater, the compound may be those having differentoxyalkylene units, that is, copolymerized oxyalkylene units which forinstance have 1-50, preferably 1-20 oxyethylene units and 1-50,preferably 1-20 oxypropylene units. Specific examples of such compoundsare (ethylene.propylene) glycol methacrylate, ethoxypoly(ethylene.propylene) glycol methacrylate, methoxypoly(ethylene.propylene) glycol methacrylate, methoxypoly(ethylene.propylene) glycol acrylate, ethoxypoly methoxypoly(ethylene.propylene) glycol acrylate and mixtures thereof.

The polyfunctional acryloyl-modified polyalkylene oxide may be abifunctional acryloyl-modified polyalkylene oxide represented by theformula

wherein R³¹, R³², R³³ and R³⁴ are each hydrogen and a C₁-C₅ alkyl groupand k is an integer of 1 or greater; or a polyfunctionalacryloyl-modified polyalkylene oxide having more than three functionalgroups represented by the formula

wherein R³⁵, R³⁶ and R₃₇ are each hydrogen and a C₁-C₅) alkyl group, lis an integer of 1 or greater, m is an integer from 2 to 4 and L is aconnecting group of valence indicated by m.

In formula (18), R³¹, R³², R³³ and R³⁴ are each hydrogen or a C₁-C₅alkyl group, such as methyl, ethyl, i-propyl, n-propyl, n-butyl,t-butyl, t-butyl and n-pentyl among which preferred are hydrogen andparticularly preferred is methyl.

The letter “k” in formula (18) is an integer of 1 or greater, usuallyfrom 1 to 100, preferably from 2 to 50, more preferably from 2 to 30.Preferred examples of compounds of formula (19) are those having 1-100,preferably 2-50, more preferably 1-20 oxyalkylene units such aspolyethylene glycol diacrylate, polypropylene glycol dimethacrylate,polyethylene glycol diacrylate, polypropylene glycol dimethacrylate andmixtures thereof.

If k is 2 or greater, the compounds of formula (18) may be those havingdifferent oxyalkylene units, that is, polymerized oxyalkylene unithaving 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20oxypropylene units, such as poly(ethylene.propylene)glycoldimethacrylate, poly(ethylene.propylene)glycol diacrylate and mixturesthereof.

In formula (19), R³⁵, R³⁶ and R³⁷ are each hydrogen or a C₁-C₅ alkylgroup, such as methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl andn-pentyl. Particularly preferred for R³⁵, R³⁶ and R³⁷ are hydrogen and amethyl group.

The letter “l” is an integer of 1 or greater, usually from 1 to 100,preferably from 2 to 50 and more preferably from 2 to 30.

The letter “m” indicates the number of connecting group “L” and is aninteger from 2 to 4.

Connecting group “L” is a divalent, trivalent or quatravalenthydrocarbon group having 1-30, preferably 1-20 carbon atoms.

Such divalent hydrocarbon groups may be alkylene, arylene, arylalkylene,alkylarylene and hydrocarbon groups having those groups as the baseskeleton. Specific examples of such hydrocarbon groups are thoserepresented by the following formulae

Such trivalent hydrocarbon groups may be alkyltryl, aryltryl,arylalkyltryl, alkylaryltryl and hydrocarbon groups having those groupsas the base skeleton. Specific examples of such hydrocarbon groups arethose represented by the following formulae:

Such quatravalent hydrocarbon groups may be alkyltetraryl, aryltetraryl,arylalkyltetraryl, alkylaryltetraryl and hydrocarbon groups having thosegroups as the base skeleton. Specific examples of such hydrocarbongroups are those represented by the following formulae:

Specific examples of compounds of formula (20) are those having 1-100,preferably 2-50, more preferably 1-20 of an oxyalkylene units such astrimethylolpropanetri(polyethylene glycol acrylate),trimethylolpropanetri(polyethylene glycol methaacrylate),trimethylolpropanetri(polypropylene glycol acrylate),trimethylolpropanetri(polypropylene glycol methaacrylate),tetramethylolmethanetetra(polyethylene glycol acrylate),tetramethylolmethanetetra(polyethylene glycol methaacrylate)tetramethylolmethanetetra(polypropylene glycol acrylate),tetramethylolmethanetetra(polypropylene glycol methaacrylate),2,2-bis[4-(acryloxypolyethoxy)phenyl]propane,2,2-bis[4-(methaacryloxypolyethoxy)phenyl]propane,2,2-bis[4-(acryloxypolyisopropoxy)phenyl]propane,2,2-bis[4-(methaacryloxypolyisopropoxy)phenyl]propane and mixturesthereof.

If l is 2 or greater, compounds of formula (20) may be those havingdifferent oxyalkylene units, that is, polymerized oxyalkylene unitshaving 1-50, preferably 1-20 of oxyethylene units and 1-50, preferably1-20 oxypropylene units. Specific examples of such compounds includetrimethyloipropaneti(poly(ethylene.propylene)glycol acrylate),trimethylolpropanetri(poly(ethylene.propylene)glycol methaacrylate),tetramethylolmethanetetra(poly(ethylene.propylene)glycol acrylate),tetramethylolmethanetetra(poly(ethylene.propylene)glycol acrylate) andmixtures thereof.

There may be used the difunctional acryloyl-modified polyalkyleneoxideof formula (18) and the polyfunctional acryloyl-modifiedpolyalkyleneoxide of formula (19) in combination. When these compoundsare used in combination, the weight ratio of the compound of formula(18) to that of formula (19) is in the range from 0.01/99.9 to99.9/0.01, preferably from 1/99 to 99/1 and more preferably from 20/80to 80/20.

The above-described organic polar solvent should be added in an amountof 50-800, preferably 100-500 weight percent based on the weight of thepolyfunctional acryloyl-modified polyalkyleneoxide. The above-describedsupporting electrolyte should be added in an amount of 1-30, preferably3-20 weight percent based on the total weight of the polyfunctionalacryloyl-modified polyalkyleneoxide and the organic polar solvent.

Similarly to Composition (A), if necessary, cross-linkers orpolymerization initiators may be added to Composition (B). Suchcomponents should be added in an amount of 0.005-5, preferably 0.01-3weight percent based on the total weight of the polyfunctionalacryloyl-modified polyalkylene oxide.

In the present invention, regardless of whether the ion conductivesubstance is liquid, gelatinized liquid or solid, an ion conductivesubstance layer is formed using a dispersion obtained by dispersing aspecified electrochromic substance into the ion conductive substance.

An electrochromic substance which is a requisite component in thepresent invention and is dispersed into the ion conductive substance,typically the above-described Compositions (A) or (B), is a compoundrepresented by the formula

wherein X⁻ and Y⁻ are each a counter anion and may be the same ordifferent and an anion selected from the group consisting of a halogenanion, ClO₄ ⁻, BF₄ ⁻, PF₄ ⁻, CH₃COO⁻ and CH₃(C₅H₄)SO₃ ⁻ and R1 and R2may be the same or different and are each a hydrocarbon group havingfrom 1 to 20 carbon atoms.

The halogen anion may be F⁻, Cl⁻, Br⁻ and I⁻. In formula (1), R¹ and R²are each independently a hydrocarbon group having from 1 to 20,preferably 1 to 12 carbon atoms and may be the same or different.Specific examples of the hydrocarbon group are an alkyl group, anaralkyl group or an aryl group, and preferably an alkyl group andaralkyl group. Specific examples of such an alkyl group are methyl,ethyl, n-propyl, i-propyl, n-butyl, i-butyl and n-hexyl groups. Specificexamples of such an aralkyl group are benzyl,phenetyl, phenylpropyl,trimethyl and ethylphenylmethyl groups.

Specific examples of a compound having a viologen structure of formula(1) are N,N′-diheptylbipyiidiniumdibromide,

N,N′-diheptylbipyridiniumdichloride,

N,N′-diheptylbipyridiniumdiperchlorate,

N,N′- diheptylbipyridiniumtetraphloroborate,

N,N′-diheptylbipyridiniumhexaphlorophosphate,

N,N′-dihexylbipyridiniumdibromide, N,N′-dihexylbipyridiniumdichloride,

N,N′-dihexylbipyridiniumdiperchlorate,

N,N′- dihexylbipyridiniumtetraphloroborate,

N,N′- dihexylbipyridiniumdihexaphlorophosph ate,

N,N′-dipropylbipyridiniumdibromide, N,N′-dipropylbipyridiniumdichloride,

N,N′-dipropylbipylidiniumdiperchlorate,

N,N′- dipropylbipyridiniumtetraphloroborate,

N,N′-dipropylbipyrndiniumdihexaphlorophosphate,

N,N′-dibenzylbipynidiniumdibromide,

N,N′-dibenzylbipyridiniumperchlorate,

N,N′-dibenzylbipyridiniumtetraphloroborate,

N,N′- dibenzylbipyiidiniumdihexaphlorophosphate,

N-heptyl-N′-benzylbipryridiniumdiperchlorate,

N-heptyl-N′-benzylbipryridiniumditetraphloroborate,

N-heptyl-N′-benzylbipryridinumdibromide,

N-heptyl-N′-benzylbipryidiniumdichloride,

N-heptyl-N′-methylpyridiniumdibromide and

N-heptyl-N′-methylpyridiniumdichloride.

Although the concentration of an electrochromic substance of formula (1)in an ion conductive substance layer is arbitrarily selected. However,it is within the range of from 0.00001 to 50 percent by weight,preferably 0.0001 to 30 percent by weight and more preferably 0.001 to10 percent by weight.

If necessary, an electrochromic substance of formula (1) may be dopedwith a compound facilitating coloration. Alternatively, anelectrochromic substance and an electron donating compound may coexistin an ion conductive substance layer.

The ion conductive substance layer of the electrochromic deviceaccording to the present invention is formed from an ion conductivesubstance containing an electrochromic substance of formula (1)dispersed therein.

Any suitable method can be employed for forming the ion conductivesubstance layer. When a liquid or gelatinized liquid ion conductivesubstance is used, the ion conductive substance containing anelectrochromic substance dispersed therein is injected into the spaceprovided between two electrically conductive substrates, i.e. counterconductive substrates, placed, facing each other and then sealed at theedges of the opposed surfaces, by vacuum injection, atmosphericinjection or a meniscus method. Alternatively, when using a specifictype of ion conductive substance, a method can be employed in which anion conductive substance layer containing an electrochromic substance isformed on one of the electrically conductive substrates by sputtering,evaporation or a sol-gel method and the substrate is put together withthe other substrate. Further alternatively, an electrochromic deviceaccording to the present invention can be obtained by inserting afilm-like ion conductive substance containing an electrochromicsubstance between a pair of glasses to form a laminated glass.

When a solid ion conductive substance, particularly the above-describedComposition A or B is used, a method can be employed in which thecomposition in an unsolidified state is inserted into the space betweenthe counter conductive substrates with their peripheral edges beingsealed, by vacuum injection, atmospheric injection or a meniscus methodand is cured in a suitable manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an electrochromic device accordingto the invention.

FIG. 2 is a cross-sectional view of an electrochromic mirror according

DETAILED DESCRIPTION OF THE INVENTION

The structure of an electrochromic device according to the presentinvention is now described taken in connection with FIG. 1.

The electrochromic mirror shown in FIG. 1 is composed of two transparentelectrically conductive substrates each consisting of a transparentsubstrate (1) and a transparent electrode layer (2) formed thereon andplaced in opposed relation such that the transparent electrode layersface toward each other and an electrochromic substance-containing ionconductive substance layer (3) disposed between the transparentelectrode layers.

The electrochromic device in FIG. 1 is produced by the followingprocedures. Two transparent conductive substrates are produced byforming a transparent electrode layer (2) on one surface of each of twotransparent substrates (1). The two transparent electrically conductivesubstrates thus produced are placed in opposed relation such that thetransparent electrode layer (2) face each other, spaced 1-1,000 μm apartand sealed at their edges with a sealant (6), leaving a portion used foran inlet, thereby forming a empty cell. Subsequently, an ion conductivematerial having a viologen-structure compound dispersed therein isinjected through the inlet into the cell, followed by sealing the inletthereby producing an electrochromic device.

When the ion conductive substance layer (3) is formed using CompositionA or B containing an electrochromic substance dispersed therein, thecomposition is usually cured after being injected into the space betweenconductive substrates. Although not restricted, Composition A or B iscured with light or heat or by being injected into the cell immediatelyafter mixed with a reactive liquid which is cures with the progress oftime. The inlet of the cell may be sealed in a suitable manner.

When the two substrates are placed, facing each other, a spacer may beinserted therebetween so as to provide a space at a fixed distanceapart. No particular limitation is imposed on such a spacer. There maybe used a spacer in the form of beads or a sheet. The spacer may beinserted between the conductive substrates facing each other or providedby forming the protrusions of an insulate material on the electrode ofan electric conductive substrate.

Although FIG. 1 shows a typical example of the structure of theinventive electrochromic device, it may be provided with an ultravioletblocking layer such as an ultraviolet reflective layer and anultraviolet absorbing layer, an overcoat layer arranged to protect theelement entirely or the surface of each of the films or layers and areflective plate to be used as a antiglare mirror. The ultravioletblocking layer is preferably disposed either on the outer side of one oftransparent substrates (1) or between a transparent electrode layer (2)and the ion conductive substance layer (3), while the overcoat layer ispreferably disposed on the outer side of one of transparent substrates(1). The reflective plate is generally disposed on the outer side of oneof transparent substrates (1). If a reflective plate has electricalconductivity, it can be replaced for the transparent electrode layer(2).

An electrochromic mirror as shown in FIG. 2 has a structure constitutedby replacing one of the two transparent conductive substrates with thetransparent electrodes (2) of the electrochromic device shown in FIG. 1with a conductive substrate composed of a substrate (5) and a reflectivepalladium electrode layer (4).

Because the electrochromic device according to the present invention hasa specified electrochromic compound contained in the ion conductivesubstance, it is quick in response and can easily be adjusted incoloration density with sufficient durability. Furthermore, theinventive electrochromic device can be easily manufactured at arelatively low cost. It is also possible to produce a large-sizedelectrochromic device with an enhanced safety because of capability ofusing a solid electrolyte as an ion conductive material layer which isfree from scattering.

For the reasons described above, the electrochromic device according tothe present invention is suitably applicable to light controllingwindows for buildings and for vehicles such as automobiles, lightcontrolling device for decoration and partitions and antiglare mirrorsfor automobiles.

The present invention is now described in further detail with referenceto Examples, which are given only by way of illustration and are notintended for limiting the invention.

EXAMPLE 1 (1) Synthesis of an Electrochromic Substance (ViologenCompound)

In a flask, 3.12 g (20 mmol) of bipyridyl was dissolved in 1000 mlacetnitrile, and 7.16 g (40 mmol) of n-heptylbromide was added thereto.

The mixture was reacted at the reflux temperature of acetnitrile for 12hours and the precipitated solid product was filtrated and dried therebyobtaining 8.74 g (17 mmol) of N,N′-diheptylbipyridiniumdibromide.

(2) Preparation of an Electrochromic Device

An epoxy-based resin was applied in the form of lines on the edges,except a portion thereof, of the surface of an ITO transparent electrodecoated over a substrate. Onto this substrate, an ITO-coated transparentsubstrate is placed such that both of the ITO surfaces face each otherwhile being pressed so as to cure the adhesive, thereby to provide anempty cell with an inlet.

On the other hand, a homogenous solution was obtained by adding 0.4 g oflithium perchlorate to a mixed solution of 1.0 g of methoxypolyethyleneglycol monomethacrylate (oxyethylene unit number: 4) manufactured bySHIN NAKAMURA CHEMICAL CO., LTD. under the trade name of MEO4, 0.02 g ofpolyethylene glycol dimethacrylate (oxyethylene unit number: 9)manufactured by SHIN NAKAMURA CHEMICAL CO., LTD. under the trade name of9G and 4.0 g of γ-butylolactone. To the homogenous solution was added0.02 g of 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-onmanufactured by Merk Co,. Ltd., under the name of “Darocure-1116” as aphotopolymerization initiator in a dark room thereby obtaining ahomogeneous solution. To the resulting homogeneous solution were added1.00 g (1.84 mmol) of N,N′-diheptylbipyridiniumdibromide obtained in (1)above and 0.442 g (1.84 mmol) of N,N,N′,N′-tetramethylbenzidinemanufactured by Tokyo Kasei Co., Ltd. and the mixture was uniformalizedand then injected as an electrolyte precursor into the cell obtainedabove through the inlet after being deaerated.

After the inlet port was sealed with an epoxy sealant, the electrolyteprecursor in the cell was cured by exposing the side of the transparentsubstrate to fluorescent light so as to form a solid electrolyte therebyobtaining an all solid type electrochromic device of the structure.

The element when assembled was not colored and had a transmittance ofabout 90%. The element was quick in response to an application of anelectric voltage and exhibited excellent electrochromic properties.Namely, the mirror was colored green upon an application of a voltage of1.5 V and was about 20% in a transmittance of 633 nm wavelength oflight.

EXAMPLE 2 (1) Synthesis of an Electrochromic Substance (a ViologenCompound)

In a flask, 3.12 g (20 mmol) of bipyridyl was dissolved in 1000 mlmethanol, and 7.16 g (40 mmol) of n-heptylbromide was added thereto.

The mixture was reacted at the reflux temperature of methanol for 12hours and the precipitated solid product was filtrated and dried therebyobtaining 8.00 g (16 mmol) of N,N′-dibenzylbipyridiniumdibromide.

(2) Preparation of an Electrochromic Mirror

An epoxy-based resin was applied in the form of lines on the edges,except a portion thereof, of the surface of a palladium film layerformed as a highly reflective electrode over a substrate. Onto thissubstrate, an SnO₂ ⁻ coated transparent glass substrate is placed suchthat the SnO₂ surface face the palladium surface while being pressed soas to cure the adhesive, thereby to provide an empty cell with an inlet.

On the other hand, a homogenous solution was obtained by adding 0.4 g oflithium perchlorate to a mixed solution of 1.0 g of methoxypolyethyleneglycol monomethacrylate (oxyethylene unit number: 4) manufactured bySHIN NAKAMURA CHEMICAL CO., LTD. under the trade name of MEO4, 0.02 g ofpolyethylene glycol dimethacrylate (oxyethylene unit number: 9)manufactured by SHIN NAKAMURA CHEMICAL CO., LTD. under the trade name of9G and 4.0 g of γ-butylolactone. To the homogenous solution was added0.02 g of 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-onmanufactured by Merk Co,. Ltd., under the name of “Darocure-1116” as aphotopolymerization initiator and 2 grams ofN,N′-dibenzylbipyridiniumdibromide obtained in (1) above in a dark roomthereby obtaining a homogeneous solution again. The resultinghomogeneous solution was then injected as an electrolyte precursor intothe cell obtained above through the inlet after being deaerated.

After the inlet port was sealed with an epoxy sealant, the electrolyteprecursor in the cell was cured by exposing the side of the transparentsubstrate to fluorescent light so as to form a electrochromic polymericsolid electrolyte thereby obtaining an all solid type electrochromicmirror of the structure as shown in FIG. 2.

The element when assembled was not colored and had a reflectance ofabout 85%. The mirror was quick in response to an application of anelectric voltage and exhibited excellent electrochromic properties. Themirror was colored green upon an application of a voltage of 1.5 V andhad a reflectance of about 15%.

We claim:
 1. An electrochromic device comprising two electricallyconductive substrates, at least one of which is transparent, and an ionconductive substance layer disposed therebetween and comprising amixture obtained by dispersing an electrochromic substance representedby formula (1) below into a composition containing a monofunctionalacryloyl-modified polyalkylene oxide represented by formula (17) and apolyfunctional acryloyl-modified polyalkylene oxide represented byformula (18) or (19), a polar solvent and a supporting electrolyte;formula (1) being represented by

wherein X⁻ and Y⁻ are the same or different and are each a counter anionselected from the group consisting of a halogen anion, ClO₄ ⁻, BF₄ ⁻,PF₄ ⁻, CH₃COO⁻ and CH₃(C₆H₄)SO₃ ⁻ and R¹ and R² are the same ordifferent and are each a hydrocarbon group having from 1 to 20 carbonatoms; formula (17) being represented by

wherein R²⁷, R²⁸, and R²⁹ are each selected from the group consisting ofhydrogen and an alkyl group having 1 to 5 carbon atoms, R³⁰ is an alkylgroup having 1 to 5 carbon atoms, and j is an integer of 2 to 30;formula (18) being represented by

wherein R³¹, R³², R³³, and R³⁴ are each selected from the groupconsisting of hydrogen and an alkyl group having 1 to 5 carbon atoms,and k is an integer of 2 to 30; and formula (19) being represented by

wherein R³⁵, R³⁶, and R³⁷ are each selected from the group consisting ofhydrogen and an alkyl group having 1 to 5 carbon atoms, l is an integerof 2 to 30, m is an integer of 2 to 4 and L is a connecting group havinga valence corresponding to m.
 2. The electrochromic device according toclaim 1 wherein the electrochromic substance of formula (1) is selectedfrom the group consisting of N,N′-diheptylbipyridiniumdibromide,N,N′-diheptylbipyridiniumdichloride,N,N′-diheptylbipyridiniumdiperchlorate,N,N′-diheptylbipyridiniumtetrafluoroborate,N,N′-diheptylbipyridiniumhexafluorophosphate, N,N-dihexylbipyridiniumdibromide, N,N′-dihexylbipyridiniumdichloride,N,N′-dihexylbipyridiniumdiperchlorate,N,N′-dihexylbipyridiniumtetrafluoroborate,N,N′-dihexylbipyridiniumdihexafluorophosphate,N,N′-dipropylbipyridiniumdibromide, N,N′-dipropylbipyridiniumdichloride,N,N′-dipropylbipyridiniumdiperchlorate,N,N′-dipropylbipyridiniumtetrafluoroborate,N,N′-dipropylbipyridiniumdihexafluorophosphate,N,N′-dibenzylbipyridiniumdibromide,N,N′-dibenzylbipyridiniumperchlorate,N,N′-dibenzylbipyridiniumtetrafluoroborate,N,N′-dibenzylbipyridiniumdihexafluorophosphate,N-heptyl-N′-benzylbipyridiniumdiperchlorate,N-heptyl-N′-benzylbipyridiniumditetrafluoroborate,N-heptyl-N′-benzylbipyridiniumdibromide,N-heptyl-N′-benzylbipyridiniumdichloride,N-heptyl-N′-methylpyridiniumdibromide andN-heptyl-N′-methylpyridiniumdlchloride.
 3. By The electrochromic deviceaccording to claim 1 wherein the polar solvent is an organic polarsolvent selected from the group consisting of methanol, ethanol,propylene carbonate, ethylene carbonate, dimethylsulfoxide,dimethoxyethane, acetonitrile, γ-butyrolactone, γ-valerolactone,sulforan, dimethylformamide, dimethoxyethane, tetrahydrofuran,propionitrile, glutaronitrile, adiponitrile. methoxyacetonitrile,dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane,trimethylphosphate, and polyethylene glycol.
 4. The electrochromicdevice according to claim 1 wherein the supporting electrolyte isselected from the group consisting of alkali metal salts, alkaline earthmetal salts, quaternary ammonium salts and cyclic quaternary ammoniumsalts.
 5. The electrochromic device according to claim 1 wherein anamount of the polar solvent contained in the layer is in a range of 100to 800 weight % based on a total amount of the monofunctionalacryloyl-modified polyalkylene oxide and the polyfunctionalacryloyl-modified polyalkylene oxide.
 6. An electrochromic devicecomprising two conductive substrates, at least one of which istransparent, and an ion conductive substance layer disposed therebetweenand containing an electrochromic substance represented by the formula(1)

wherein X⁻ and Y⁻ are the same or different and are each a counter anionselected from the group consisting of a halogen anion, ClO₄ ⁻, BF₄ ⁻,PF₄ ⁻, CH₃COO⁻ and CH₃(C₈H₄)SO₃ ⁻ and R¹ and R² are the same ordifferent and are each a hydrocarbon group having from 1 to 20 carbonatoms and wherein the ion conductive substance comprises a mixtureobtained by dispersing the electrochromic substance into a compositioncontaining an urethaneacrylate represented by formula (2) below, a polarsolvent and a supporting electrolyte; formula (2) being represented bythe formula

wherein R⁶ and R⁷ are the same or different and are each a group offormula (3), (4) or (5) below, R⁸ and R⁹ are the same or different andare each a C₁-C₂₀, preferably C₂-C₁₂ divalent hydrocarbon residue, Y isselected from a polyether unit, a polyester unit, a polycarbonate unitand mixed units thereof and b is an integer from 1 to 100, preferably 1to 50 and more preferably 1 to 20; formulae (3), (4) and (5) beingrepresented by the formulae

wherein R¹⁰, R¹¹ and R¹² are the same or different and are each ahydrogen atom or a C₁-C₃ alkyl group and R¹³ is a C₁-C₂₀, preferablyC₂-C₈ organic residue of divalent through quatervalent.